PSI - Issue 52

Sairam Neridu et al. / Procedia Structural Integrity 52 (2024) 267–279 Sairam Neridu/ Structural Integrity Procedia 00 (2019) 000 – 000

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reinforcing materials, resulting in increased strength. Testing the concrete at an early age, such as 7 or 14 days after casting, can also result in higher rebound hammer test strength, as concrete gains most of its strength in the first few weeks after casting.

Table 4. Results of Compressive Strength Test on extracted cores

Core Length

Core Dia (d) (mm)

Corrected Cyl. Comp. Strength (N/sq.mm)

Equivalent Cube Comp. Strength ++ (N/sq.mm)

Core Compressive Strength (N/sq.mm)

Correction factor for (l/d) ratio +

Core Weight (kg.)

Sl.

l/d ratio

Location

** (l) (mm)

Area

Load

No.

Wall Pier at 1.75m from RHS end and 1.1m from the raft Wall Pier at 7.7m from LHS end and 1.98m from the raft Wall Pier at 0.5m from LHS end and 0.85m from the raft

19.13

1

152

94

2.316

110.9 15.980

1.62

0.958

15.31

6939.8

17.85

2

155

94

2.368

103.1 14.856

1.65

0.961

14.28

6939.8

20.37

154

94

2.343

117.8 16.975

1.64

0.960

16.30

6939.8

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The results of the compressive strength tests performed on extracted core samples from three different locations of the wall pier are presented in Table 4. The corrected cylindrical compressive strength and equivalent cube compressive strength reveal that the compressive strength of the wall pier samples ranges from 17.85 to 20.37 N/sq.mm. The lower than-designed concrete strength obtained from the compressive strength test implies that the concrete used in the construction of the bridge is of poor quality. Inadequate curing, improper placement of reinforcing steel, or inadequate consolidation during the construction process can lead to lower-than-designed concrete strength. Based on these experimental findings, it can be concluded that the concrete quality used in the construction of the bridge was unsuitable for its purpose and was unable to withstand the design live loads. Therefore, assessing the structural integrity and durability of the pier wall and designing a suitable restrengthening method is crucial to ensure the safety and longevity of the structure. The experimental data obtained from NDT testing will be instrumental in designing an appropriate restrengthening strategy to withstand the live loads on the bridge for its design life. 5.2. Numerical Analysis To analyse the deformation and stress distribution of the bridge structure ANSYS Workbench software is used figures 4. To achieve this, 3D models of bridge structures were created and subjected to design loading conditions which include dead loads, earth-filling loads, and live loads. The study considers various grades of concrete viz M15 (experimental and visual observation), M20 (experimental observation) & M30 (actual design grade) to evaluate their impact on the deformation and stress distribution of the bridge structure. The static analysis of a bridge using ANSYS software for pier walls of 300 mm and 450 mm thickness made of different grades of concrete (M15, M20, and M30) were performed, and the results are presented in table 5. The analysis results indicate that increasing the thickness of the pier wall from 300 mm to 450 mm results in lower total deformation and maximum principal stresses for all grades of concrete. This is due to the increased stiffness of the thicker pier wall, which can resist the applied loads more effectively. Static Analysis of the bridge is shown in figure 5(a) Total Deformation; 5(b) Maximum principal stresses; 5(c) Minimum Principal stresses; 5(d) Normal stresses.